FR2570290A1 - DEVICE FOR SEPARATING WATER AND STEAM FOR DRYING WET STEAM - Google Patents

Abstract

THE INVENTION RELATES TO A WATER AND VAPOR SEPARATION DEVICE FOR DRYING A WET VAPOR WHOSE INFLOW CURRENT TO THE DEVICE IS ASCENDING. THE DEVICE INCLUDES AT LEAST ONE ASSEMBLY 8 CONSTITUTES OF DRYING ELEMENTS IN A ZONE 12 IN WHICH IS A PERFORATED PANEL 11. THE PERFORATED VERTICAL PANEL 11 IS CONSTITUTED BY A DEPLOYED METAL GRID ALLOWING DEFLECTION OF THE STEAM INCIDENT 9 FLUID TO MAKE IT HORIZONTAL OR SLIGHTLY DOWN DOWN 16. THE INVENTION APPLIES, IN PARTICULAR, TO STEAM GENERATORS OF PRESSURIZED WATER NUCLEAR REACTORS.

Description

1.

  The invention relates to a separating device

  water and steam for drying wet steam and, in particular, a dryer arranged at the steam outlet in the upper part of a steam generator of a water nuclear reactor

under pressure.

  In nuclear power plants with a pressurized water reactor, the steam produced in the steam generators has a relatively low moisture content, but is excessive for this steam to be used in the turbines,

without intermediate drying.

  The steam generators of the nu-

  pressurized water-presses therefore have, in their upper part on the outlet path of the steam, drying devices which are of two types and

  arranged successively in the path of the steam.

  First, the steam enters centrifugal separators where it is rotated in a helix, the water droplets contained in the vapor separating from it by centrifugal effect before being trapped on a cylindrical wall which ensures the return of

  water by gravity in the feeding area of the gen-

steam generator.

  At the exit of the centrifugal separators, the va-

  fear undergoes a second drying, called fine drying, in

  baffle separators which produce modifications

  sudden succession of the direction of flow of the vapor. The known baffle separators of a

  very good performance, include directional gutters

  vertically associated with baffles for recovery

  ration of water separated from the steam. These gutters have straight sections in horizontal planes of hollow form, the concavity of which is directed towards the incident flow of the vapor, so that the water droplets separated from the vapor on the walls of the baffles 2.

  are stopped by the gutters, collected and directed

  by gravity towards the lower part of the sepa-

  rators and then to the generator

  of steam, via drainage ducts.

  Although these gutters significantly increase the efficiency of the baffled dryers, they nevertheless have drawbacks that make them

the use more difficult.

  First, these gutters interposed in the path of the steam, increase the pressure drop in the dryer. On the other hand, they create an area where the steam is overpressurized just upstream of the liquid film constituted by the droplets collected in the gutters. In this zone under overpressure, the vapor stream and the water droplets on the other hand have a speed practically zero, so that we are in

  presence of water particles in equilibrium with a

  fear in overpressure. These particular conditions do not favor the elimination of the flow of water

gravity.

  In addition, the vapor current is rising

  throughout the crossing of the dryers that are available

  successively one above the other. This updraft causes the water droplets upwards, in the areas upstream of the gutters, to counteract the film of liquid, which slows down its flow.

gravity flow.

  It has been proposed to produce the baffled dryers in the form of assemblies consisting of a perforated vertical panel with which the incident vapor flow which contacts, after passing through the perforated panel, comes into contact with an area containing the baffles and the baffles.

  gutters for water recovery. The panel

  The drilled hole constituting the inlet wall of the dryer creates a pressure drop on the flow of steam and inflects this vapor stream downwards. For example, as perforated panel for entering the steam, a plate having bores having a size and

  chosen to substantially modify the listening

  steam without increasing the loss of charge too much. Such deflector devices however remain

very limited efficiency.

  It has also been proposed to use panels constituted by a frame in which series of parallel strips inclined downwards in the direction of flow of the louver type vapor have been placed. Such panels can be highly effective in

  concerning the efffection of the flow of steam, but their

  is difficult when they are destined to come

  in contact with a very high temperature vapor

  at a very high speed. Whatever the manufacturing process of these panels, we can not guarantee a very

  - good resistance and a long service life.

  The object of the invention is therefore to propose a

  water and steam separation device for the se-

  drying of a wet vapor whose flow of arrival to the separating device is ascending, comprising at least one assembly interposed on the course of the steam

  consisting of drying elements and a green panel

  perforated tical one of which face, or face of entry, receives the wet steam which opens, after passing through the perforated panel, in an area containing the drying elements, including deflection baffles of the vapor flow and recovery gutters l water separated from the steam arranged vertically and so that the horizontal cross section has a hollow portion directed towards the incident flow of vapor, disposizif which is of great efficiency, simple embodiment and a very

high mechanical strength.

  4. For this purpose, the perforated vertical panel is

  consisting of an expanded metal grille whose

  lules allowing the passage of steam are limited by slats inclined downwards in the direction of passage of the steam for the deflection of this va-

  fear, so that his journey is substantially

  zontal or slightly downward at the moment o

  it comes in contact with the drying elements.

  In order to understand the invention, we will now describe; by way of nonlimiting example, a device for separating water and steam according to the invention, used for drying wet steam

  generated by a steam generator of a nuclear reactor

pressurized water area.

  Fig. 1 is a sectional view through a green plane.

  tical of the upper part enclosing the devices

  dryers, a steam generator of a nuclear reactor

  pressurized water area; FIG. 2 is a sectional view through a vertical plane of a drying assembly of a baffled dryer of the steam generator shown in FIG. 1; FIG. 3 is a front view of an expanded metal gate portion constituting the inlet wall of the drying assembly shown in FIG. 2; FIG. 3A is a sectional view along A-A of FIG. 3; FIG. 4 is a sectional view through a plane

  of a part of the zone containing the ele-

  drying elements of the assembly shown in FIG. 2; FIG. 5 is a view similar to FIG. 4, an embodiment variant of the zone enclosing the

drying elements.

  In FIG. 1, we see the upper part of a steam generator whose outer shell 1

  has a diameter greater than the diameter of the lower part

  5. top of the steam generator containing the beam

  of which we see the upper part 2 in FIG. 1.

  The beam 2 is constituted by a set

  of tubes inside which water circulates under pres-

  from the nuclear reactor vessel for the heating of the feed water of the generator of

  steam, then vaporization, the steam produced penetrates

  in the upper part 1 of the generator of

  fear following a virtually vertical path symbolized

by the arrows 3.

  The envelope 1 of the upper part of the gen-

  The steam separator contains the centrifugal separators such as 4 and two stages of baffle dryers Sa b, placed one above the other. The vapor coming out of the beam enters the separators first.

  where its path becomes helicoidal, a part

  water droplets transported by the vapor then deposited on the cylindrical inner wall of the centrifugal separators which ensures the return of this water in the zone 6 of water supply of the generator of

  steam at the level of which is placed the feed torus

  7 of the steam generator ensuring the return of

  condensed water at the exit of the turbines.

  Above the centrifugal separators 4 are arranged two stages of baffle separators 5a and 5b

  each consisting of four drying sets 8 dis-

  laid along the vertical faces of a parallelepiped

  whose layout is central, within the

  veloppe 1 from the top of the generators of

steam.

  The partially dried vapor from the sepa-

  centrifugal devices 4 comes into contact with the face

  inlet of the drying elements 8 into an updraft

  9 direction, passes through these drying elements 8

  and exits the steam generator through the tubing 10

6.

  pouring the envelope 1 at its upper part.

  In FIG. 2, we see a vertical section,

  in the direction of passage of steam, a

  8, on a larger scale than in FIG. 1.

  This element 8 has a generally parallel shape

  pipedic and comprises a perforated inlet wall 11, a drying zone 12 and a recovery zone of

water 13.

  As it is visible in Figs. 3 and 3a, the panel 11 is constituted by a expanded metal grid whose cells 14 are diamond-shaped and are limited by slats 15 inclined towards the

  down in the direction crossed by the steam.

  Such an expanded metal grille is a

  duit known in itself and can be obtained by

  page of a sheet followed by stretching during which the separation strips of the cut cells take an identical inclination with respect to the plane of the sheet, to form lamellae regularly distributed in the planes of cross section of the sheet according to the directions main cells of the network, as it

is visible in FIG. 3a.

  The expanded metal grille thus presents a

  sloped structure similar to the structure

  of a sloped panel of the persian type.

  born. Such a structure produces a deflection of a fluid stream passing through these cells 14, as can be seen in FIG. 3a, for the incident steam flow 9 whose direction of displacement 16 after

  crossing the grid 11 is substantially horizontal.

  The grid is obviously arranged in such a way that

  males 15 are inclined downwards in the direction of

crossing the steam flow.

  7. The amplitude of the deflection caused by the

  grill 11 depends on several parameters and, in

  of the width 1 of the metal strips between two cuts of the sheet, called straps, and the size of the mesh 14, both in the longitudinal direction corresponding to the length of the blanks of the sheet, and in the transverse direction corresponding to the drawing direction of this sheet

to form the grid.

  By playing on these various parameters, it is possible to determine a sufficient deflection of the incident steam flow to make its path horizontal (direction 16) or even slightly downward (direction 17) in the drying zone 12 disposed beyond the

grid 11.

  However, the pressure drop of the device increases

  when changing the settings of the grid for

increase the deflection.

  It will therefore be necessary to choose structure characteristics of the grid to obtain a flow of

  steam moving in a direction close to the horizon

  zonal in zone 12, while limiting the loss of

charge to an acceptable value.

  In FIG. 4, we see a portion of the horizontal section of the zone 12 in which are arranged baffles 20 constituted by vertical plates folded or connected constituting dihedral angles

  successively arranged in one direction or the other,

  sins of 90. The baffles 20 are arranged one after the other parallel in the longitudinal direction of the drying assembly, that is to say in the horizontal direction parallel to the panel 11

  constituting the entrance face of this drying assembly.

  The baffles 20 are arranged to interpose on the path of the steam 16 inside the zone 8.

  12, in a substantially horizontal direction

  tale. At each of the dihedral angles at 90

  baffles, is fixed a vertical gutter 21, al-

  at least one side and the other of the baffle 20. The straight sections of the gutters 21 are in the form of rectangles, hollow and open to the incident flow of the vapor 16. The gutters 21 are used to stop the droplets of water deposited by the steam on the walls of the baffles and to send the water thus collected to the lower part of the drying assembly in the recovery zone 13. The gutters 21 are also responsible for the formation of zones 23 o the steam is in excess pressure, immediately upstream of the water 24 collected by the trough 21. In this zone 23, the liquid droplets and the vapor

  have a zero velocity component in the horizontal plane

  zontal. This, however, has no adverse effect on the gravitational flow of the liquid film 24, since the flow of directional vapor 16 is either horizontal,

  slightly inclined downwards, thanks to the deflec-

  expanded metal sheet 11.

  It is thus seen that one of the advantages of the device according to the invention is to allow the use of drying elements comprising baffles and vertical gutters, in very good conditions.

  efficiency. These advantages are achieved through a

  of deflection of a very great facility of

  and a very good resistance, since it is obtained from a sheet by a punching operation

  followed by stretching, without the need for welding. This element

  The monobloc version therefore has a much better resistance

  and a much better reliability than an element

  seemed like a panel louver type finned reported. 9.

  In FIG. 5, we see a variant of reali-

  the drying area, baffles and

  The incident flux stream 16 is deflected by successive elements 26 whose semicircle sections are open towards the vertical plane 25. incident steam flow. The elements 26 also constitute recovery gutters of the water film 27 constituted

  from the droplets deposited on their surface

  dull. In the same way as above, the gravitational flow of the film 27 is only slightly hampered or even facilitated by the flow of steam 16 whose direction of travel is horizontal or slightly inclined towards

the bottom.

  The invention is not limited to the method of

  which has just been described. This is how we can

  a separation device comprising an expanded metal entrance panel and drying devices (baffles and gutters) of a type different from those described, baffles and gutters being constituted either by different elements , either by

the same elements.

  One can imagine the use of an expanded metal grid having cells of a different shape

  of the diamond shape that has been described.

  The dimensions of the grid will be defined according to the desirable deflection of the vapor flow and the acceptable pressure drop under the conditions

of use of the device.

  Finally, the device according to the invention is

  not only to the steam generators of the reac-

  nuclear power plants, but also to

  other types of steam generators, even at

  different plants of steam generators in the-

  10. a moist vapor is obtained whose current is

output is ascending.

11.

Claims (3)

  1. Device for separating water and steam   for drying wet steam with   the separation device is ascending, including   at least one assembly (8) interposed on the path of the steam constituted by drying elements (20, 21, 26) and a perforated vertical panel (11) having a face or inlet face receiving the wet vapor which opens, after passing through the perforated panel (11) in   an area (12) containing the drying elements comprises   baffles (20, 26) for diverting the flow of steam   and gutters (21, 26) for collecting the separated water   of the vapor arranged vertically and so that their horizontal cross-section   hollow directed towards the incident steam flow (16), which is   characterized in that the perforated vertical panel (11) is constituted by an expanded metal grid whose   cells (14) allowing the passage of steam are   mitered by slats (15) inclined downwards in the direction of passage of the steam for the deflection of   this steam, so that its course is sensitive-   horizontal or slightly downward   when it comes into contact with the elements of chage (20, 21, 26).   2. Device for separating water and steam according to claim 1, characterized in that the expanded metal grid (11) comprises cells (14) shaped lozenges whose large diagonals are horizontal.   3. Device for separating water and steam   according to any one of claims 1 or 2,   characterized in that it is arranged in the wet vapor outlet path in the upper part (1) of a steam generator of a water nuclear reactor under pressure.